The term "z-wave controller" is often used ambiguously to refer to the hardware that's the "master" node of a z-wave network (usually with node ID 1; the USB z-wave dongle) or a high level device, often with a built in web server with lots of added features to facilitate easy user interaction with the z-wave network. Z-Command falls into the latter category. Sometimes, the z-wave controller node (the former) is built into the high level device (the latter).

Depending on the product variant you order, you can buy Z-Command with or without a z-stick (the z-wave controller node). This sometimes makes sense because you can use other types of USB z-wave controllers with Z-Command aside from the bundled Gen 5 Aeon Labs Z-Stick.

As for ease of linking other z-wave devices to the network by being able to disconnect the USB z-wave controller and walking up to other z-wave devices, that is a unique feature of the Aeon Labs Z-Stick and not a z-wave feature per se.